Freak weather events spiked this year: Data
India has already experienced more “extreme rainfall periods” in 2019 as compared to 2018, but there are also large pockets of the country affected by drought-like conditions due to the unequal distribution of rainfall.Updated: Aug 17, 2019 08:54 IST
India has already experienced more “extreme rainfall periods” in 2019 as compared to 2018, but there are also large pockets of the country affected by drought-like conditions due to the unequal distribution of rainfall, according to data from the India Meteorological Department (IMD) that provides insights into the vagaries of the Indian weather system.
Experts say this is because low-intensity precipitation, vital to recharge the groundwater and check drought is falling in several areas, though the overall rainfall in India has remained “normal” because of very high rainfall in several other areas.
According to IMD, India has experienced 10 extreme rainfall periods so far in the 2019 monsoon, leading to flooding in Kerala, north Karnataka, Maharashtra (including Mumbai), Assam, north Bihar, eastern Uttar Pradesh, south Gujarat and some parts of Punjab. In 2018, the country experienced seven such extreme weather periods. The most intense of the extreme rainfall periods in 2019 were from July 10-15, causing floods in eastern Uttar Pradesh and northern Bihar; July 25-31, leading to flooding in Assam; and August 5-10, causing floods in western coastal India, or in parts of Maharashtra, Goa, Karnataka and Kerala.
An extreme rainfall period is defined as one in which two or more “extreme rainfall events” occur within a week.
An extreme rainfall event is one in which 150mm to 200mm of rain falls in a region in a short time -- which could be a city or a cluster of villages -- in 24 hours.
The IMD daily rainfall data also shows close to 100 extreme rainfall events this year till August 12. The IMD report for 2018 monsoon had listed about 92 such extreme rainfall events that year. There is still a month of the 2019 monsoon season to go.
Some of the more severe extreme rainfall events happened in Chamoli, Uttarakhand, earlier this week, leading to the death of six people; and in Ratnagiri district of Maharashtra on July 2, when a dam breach killed 15 people. Isolated extreme rainfall events were also reported from cities such as Vadodara, Morbi and Valsad in Gujarat; Mumbai, Pune and Sangli in Maharashtra; and East Champaran in Bihar.
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An analysis of daily rainfall between 1901 and 2010 by the Indian Institute of Tropical Meteorology (IITM), Pune, showed a decadal increase of about 6% in “extreme rainfall”, events with the frequency increasing post-1981.
“The inter-annual and inter-decadal variability of extreme rain events over India is influenced by the sea surface temperature (SST) variations over the tropical India Ocean,” said the report published by earth sciences ministry secretary Madhavan Nair Rajeevan, who has worked as a scientist at IITM.
“As the climate warms in response to increases in greenhouse gases, the concentrations of water vapor are expected to increase due to higher difference in surface and atmospherictemperaturesleading to heavy rainfall,” he said.
Former director general of IMD, KJ Ramesh, said that such extreme rainfall periods and events increased this year, along with extreme heat during the summer months over parts of the Indian subcontinent. “This led to higher SST variation and a cause for more heavy rain days,” he said.
But even as extreme rainfall days have risen, which in climatology can be termed as an “exceptional year”, several regions in India are facing drought because of severely deficient rainfall.
In Madhya Pradesh, seven districts in the state are facing drought even though Malwa region is flooded because of heavy rainfall in Narmada catchment areas. The Maukaushal and Bundelkhand regions are the worst hit.
Many districts in eastern and southern Uttar Pradesh are witnessing dry weather conditions, with rainfall deficit of up to 40%, and so is the case in central and southern West Bengal. Half of Bihar, especially its southern parts, and several districts in Jharkhand, are facing dry weather conditions with rainfall deficit being over 50%.
In Maharashtra, while Satara, Sangli and Kolhapur are flooded because of incessant rains, the Marathwada region is witnessing a severe drought. Most parts of Rayalseema in Andhra Pradesh, and some districts in Tamil Nadu have got less-than-normal rainfall this monsoon till August 13.
Droughts have also been an annual affair in India between 2000 and 2018, according to data compiled by the ministry of statistics and programme implementation. In this period, the highest number of districts affected were 338 in 2009 and least were 52 in 2011. In 2019, 110 districts in India are either facing drought or drought-like conditions.
Vimal Misha, an associate professor at the Indian Institute of Technology, Gandhinagar, said that extreme weather events in India today are more visible than in the past, and its impact through higher frequency of droughts and floods is impacting everyone’s life.
“Our studies have shown that drought occurrence was rising as low intensity precipitation vital for recharge of the ground was reducing even though overall rainfall in the monsoon season has remain almost same since 1950s. Our study of 5,800 ground wells shows that ground water recharge by low intensity rainfall is vital for ground water recharge in the heavily irrigated north and south India,” he said in a 2018paper on extreme weather events in India.